JP2001233954A - Polyester, and blow molded article, sheet-like article, and stretched film made thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester excellent in controllability of crystallization during melt molding and in long-time continuous moldability; a blow molded article which has good clarity and thermal dimensional stability, exhibits a suitable shrinkage at the cap section, and, when used as a liquid container, does not cause remaining strange taste and odor to occur; and a sheet-like article and a stretched film both having good clarity and thermal dimensional stability. SOLUTION: This polyester mainly comprises repeating ethylene terephthalate units, and when it is melted at 290 deg.C for 60 min, the increase in the amount of a cyclic trimer is 0.30 wt.% or lower. In the polyester, the content of a cyclic trimer is 0.35 wt.% or lower; the average density of chips of the polyester is 1.3950 g/cm3 or higher; the density of the outer layer of the chip is 1.4030 g/cm3 or lower; and the difference in density between the central layer and the outer layer of the chip is 0.0015-0.0050 g/cm3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester, and a hollow molded article, a sheet, and a stretched film made of the polyester, and more particularly, to a crystallization control property during melt molding.
The present invention relates to a polyester having excellent long-term continuous moldability, and a molded article, a sheet, and a stretched film having excellent transparency and heat-resistant dimensional stability.

[0002]

2. Description of the Related Art Conventionally, various resins have been employed as materials for containers for seasonings, oils, beverages, cosmetics, detergents, etc., depending on the type of filling content and the purpose of use. Among these resins, polyester is excellent in mechanical strength, heat resistance, transparency, and gas barrier properties, and is therefore particularly suitable as a material for beverage filling containers such as juices, soft drinks, and carbonated drinks. Such a polyester is supplied to a molding machine such as an injection molding machine to form a preform for a hollow molded body, the preform is inserted into a mold having a predetermined shape, stretch-blown, and then the body of the bottle is heat-treated. (Heat setting) to form a hollow molded body, and further, if necessary, heat treatment (crystallization of the plug portion) of the plug portion of the bottle.

[0003] In this case, the conventional polyester contains oligomers such as cyclic trimers, and these oligomers adhere to the inner surface of the mold, the exhaust port of the mold gas, and the exhaust pipe during molding. Mold stains were likely to occur.
Such mold contamination causes surface roughness and whitening of the obtained hollow molded body. If the hollow moldings are whitened, they must be discarded. For this reason, mold contamination must be removed frequently, and there has been a problem that the productivity of the bottle is reduced. Also,
Polyester contains a by-product acetaldehyde. When the content of acetaldehyde in the polyester is large, the content of acetaldehyde in the container or other packaging material formed from the polyester also increases, which affects the flavor and odor of beverages filled in the container and the like. Therefore, various measures have conventionally been taken to reduce the acetaldehyde content in the polyester.

[0004] In recent years, hollow molded articles made of polyester, mainly polyethylene terephthalate, have come to be used as containers for low-flavor beverages such as mineral water and oolong tea. In the case of such beverages, these beverages are generally heat-filled or sterilized by heating after filling, but reducing the acetaldehyde content of the beverage container alone does not improve the flavor or odor of these contents. I understand. For metal cans for beverages, for the purpose of process simplification, hygiene, pollution prevention, etc., a method of making cans using a metal plate coated on its inner surface with a polyester film centering on polyethylene terephthalate is adopted. It has become. Also in this case, the contents are heat-sterilized at a high temperature after filling, but it has been found that the flavor and odor of the contents are not improved even if a film having a low acetaldehyde content is used.

In order to solve such a problem, the molecular weight is increased and the acetaldehyde content and the cyclic trimer are reduced by subjecting the polyester chips obtained by melt polycondensation to solid-state polymerization. The polyester is treated by the water treatment method disclosed in JP-A-3-174441.

However, when this method is carried out industrially, the use of distilled water as treatment water is disadvantageous in terms of cost. It is common to use water. However, when water treatment is performed using industrial water, there is a problem that crystallization during molding is often too early, resulting in a hollow molded body having poor transparency. In addition, there is also a problem that shrinkage of the plug portion due to crystallization of the plug portion does not fall within the standard, resulting in poor capping.

According to the study of the present inventors, this is due to the fact that at the stage of water treatment, when the content of metal-containing substances such as sodium, magnesium, calcium and silicon dioxide contained in industrial water is larger than a certain value, Fine powder mainly composed of metal-containing substances such as oxides and hydroxides of these metals floats and precipitates in the treatment water, and further adheres to the walls of the treatment tanks and piping, which further adheres to and penetrates the polyester chips. It was found that crystallization during molding was promoted, resulting in a bottle with poor transparency. Further, there have been problems such as the fine powder mainly composed of a metal-containing substance clogging the piping and making the treatment tank and the piping difficult to clean. In the water treatment stage, fines (resin fine powder) adhering to the polyester chips float and precipitate in the treated water and adhere to the walls of the treatment tanks and pipes, causing clogging of the pipes, There have also been problems such as making the cleaning of the glass difficult.

Therefore, in order to obtain a water-treated polyester which can be molded into a molded article having good transparency, ion-exchanged water obtained by treating industrial water with an ion-exchange treatment apparatus is used. There is also a method of treating the polyester with water while controlling the amount of the fine powder in the solution to a certain concentration or less, but even in this case, only a molded article having poor transparency may be obtained.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the problems of the above-mentioned conventional polyesters and hollow molded articles, sheets and stretched films made of the same, and provides crystallization controllability during melt molding and continuous continuation for a long time. Polyester excellent in formability and transparency and thermal dimensional stability obtained therefrom are good. Particularly, the shrinkage rate of the plug part of the hollow molded product is in an appropriate range, and when it is used as a liquid container, residual off-flavor and off-flavor It is an object of the present invention to provide a hollow molded article, a sheet-like material, and a stretched film, in which the occurrence of cracks is difficult.

[0010]

In order to achieve the above-mentioned object, the polyester of the present invention has a main repeating unit of ethylene terephthalate and has a temperature of 290 ° C. and a temperature of 60%.
In a polyester having a cyclic trimer increase of 0.30% by weight or less when melted for one minute, the cyclic trimer content is 0.35% by weight or less, and the average density of the polyester chips is 1.3950 g. / Cm ³ or more, the density of the outer layer of the chip is 1.4030 g / cm ³ or less, and the difference in density between the center layer and the outer layer of the chip is 0.0015 to 0.0050.
g / cm ³ .

[0011] The polyester of the present invention having the above-mentioned constitution is less likely to cause mold contamination during molding, has excellent crystallization controllability of the plug portion, and has excellent transparency, heat resistance, mechanical properties, and residual off-flavor. It can be formed into a hollow molded article, a sheet-like material, and a stretched film having a low unpleasant odor and excellent fragrance retention.

In this case, the content of the copolymerized diethylene glycol may be 1.5 to 5.0 mol% of the glycol component constituting the polyester.

In this case, the content of acetaldehyde may be 5 ppm or less.

Further, in this case, the polyester chips may contain 0.1 to 300 ppm of polyester fine having the same composition as the chips.

In this case, the chips formed after the polycondensation can be treated with treated water satisfying the following conditions (a) and (b) in a treatment tank. (A) Temperature of 40 to 120 ° C (b) Treated water including wastewater from the treatment tank

In this case, chips formed after polycondensation may be treated in a treatment tank with treated water satisfying the following condition (c). (C) Treated water having a fine powder content of 1000 ppm or less

In this case, the hollow molded body is
It can be obtained by molding the polyester described above.

In this case, the sheet-like material is
It can be obtained by molding the polyester described above.

Furthermore, in this case, the stretched film may be formed by stretching a sheet material in at least one direction.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the polyester of the present invention and hollow molded articles, sheets and stretched films comprising the same will be described below.

The polyester of the present invention is a polyester whose main repeating unit is ethylene terephthalate, preferably a linear polyester containing at least 85 mol% of ethylene terephthalate units, more preferably at least 90 mol%, particularly preferably at least 90 mol%. It is a linear polyester containing 95% or more.

The dicarboxylic acid as a copolymer component used when the polyester is a copolymer includes:
Aromatic dicarboxylic acids such as isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethane dicarboxylic acid and functional derivatives thereof, and oxy acids such as p-oxybenzoic acid and oxycaproic acid Examples thereof include acids and functional derivatives thereof, aliphatic dicarboxylic acids and functional derivatives thereof such as adipic acid, sebacic acid, succinic acid, and glutaric acid, and aliphatic dicarboxylic acids and functional derivatives thereof such as cyclohexanedicarboxylic acid.

The glycol used as a copolymer component when the polyester is a copolymer includes aliphatic glycols such as diethylene glycol, trimethylene glycol, tetramethylene glycol and neopentyl glycol, and lipids such as cyclohexanedimethanol. Cyclic glycol, bisphenol A, bisphenol A
And aromatic glycols such as alkylene oxide adducts.

Further, as the polyfunctional compound as a copolymer component used when the polyester is a copolymer, trimellitic acid, pyromellitic acid and the like can be mentioned as an acid component, and a glycol component can be used as a glycol component. Glycerin and pentaerythritol can be mentioned.
The amount of the above-mentioned copolymer component to be used must be such that the polyester maintains a substantially linear shape. Further, a monofunctional compound such as benzoic acid or naphthoic acid may be copolymerized.

The polyester is produced by, for example, directly reacting terephthalic acid with ethylene glycol and, if necessary, the above-mentioned copolymerization component to distill water and esterify the mixture, and then use an Sb compound, Ge compound or Ti compound as a polycondensation catalyst.
A direct esterification method in which polycondensation is performed under reduced pressure using one or more compounds selected from compounds, or dimethyl terephthalate is reacted with ethylene glycol and, if necessary, the copolymerization component in the presence of a transesterification catalyst. A transesterification method in which methyl alcohol is distilled off and transesterification is performed, and then polycondensation is performed mainly under reduced pressure using one or more compounds selected from Sb compounds, Ge compounds and Ti compounds as polycondensation catalysts. It is manufactured by

Examples of the Sb compound used for producing the polyester of the present invention include antimony trioxide, antimony acetate, antimony tartrate, antimony tartrate, antimony oxychloride, antimony glycolate, antimony pentoxide, triphenylantimony and the like. Can be S
The compound b has a residual Sb content of 50 to 50 in the produced polymer.
It is added so as to be in the range of 250 ppm.

Examples of the Ge compound used for producing the polyester of the present invention include amorphous germanium dioxide, crystalline germanium dioxide, germanium chloride, germanium tetraethoxide, germanium tetra-n-butoxide, germanium phosphite and the like. Can be When a Ge compound is used, the amount used is 5 to 150 ppm, preferably 10 ppm, as the amount of Ge remaining in the polyester resin.
-100 ppm, more preferably 15-70 ppm.

Examples of the Ti compound used for producing the polyester of the present invention include tetraalkyl titanates such as tetraethyl titanate, tetraisopropyl titanate, tetra-n-propyl titanate, tetra-n-butyl titanate and partial hydrolysates thereof. And titanyl oxalate, titanyl oxalate, sodium titanyl oxalate, potassium titanyl oxalate, titanyl calcium oxalate, titanyl strontium oxalate and the like, titanium oxalate compounds, titanium trimellitate, titanium sulfate, titanium chloride and the like. The Ti compound is added so that the amount of Ti remaining in the produced polyester is in the range of 0.1 to 10 ppm.

Various P compounds can be used as a stabilizer. Examples of the P compound used in the present invention include phosphoric acid, phosphorous acid, phosphonic acid, and derivatives thereof. Specific examples include phosphoric acid, trimethyl phosphate, triethyl phosphate, tributyl phosphate, triphenyl phosphate, monomethyl phosphate, dimethyl phosphate, monobutyl phosphate, dibutyl phosphate, and dibutyl phosphate. Phosphoric acid, Trimethyl phosphite, Triethyl phosphite, Tributyl phosphite, Methylphosphonic acid, Methylphosphonic acid dimethyl ester, Ethylphosphonic acid dimethylester, Phenylphosphonic acid dimethylester, Phenylphosphonic acid diethylester, Phenylphosphonic acid And diphenyl esters. These may be used alone or in combination of two or more. The P compound is added at any stage of the polyester production reaction step so that the residual amount of P in the produced polyester is in the range of 5 to 100 ppm. Further, solid-state polymerization may be performed to increase the intrinsic viscosity of the polyester and reduce the acetaldehyde content.

The above-mentioned esterification reaction, transesterification reaction, melt polycondensation reaction and solid-phase polymerization reaction may be carried out in a batch reactor or in a continuous reactor.

The intrinsic viscosity of the polyester of the present invention is preferably 0.55 to 0.90 dL / g, more preferably 0.58 to 0.88 dL / g, and still more preferably 0.6 to 0.88 dL / g.
It is in the range of 0 to 0.86 dL / g. Intrinsic viscosity 0.5
If it is less than 5 dL / g, the obtained molded product has poor mechanical properties. On the other hand, when it exceeds 0.90 dL / g, the temperature of the resin increases during melting by a molding machine or the like, and thermal decomposition becomes severe, so that free low-molecular-weight compounds that affect fragrance retention increase, Problems such as yellowing occur.

In the present invention, the shape of the polyester chip may be any of a cylinder type, a square type and a flat plate shape, and the size thereof is usually 1.5 to 4 mm in length, width and height. Range. For example, in the case of a cylinder type, it is practical that the length is about 1.5 to 4 mm and the diameter is about 1.5 to 4 mm. The tip weight is 15
A range of ３０30 mg / piece is practical.

The polyester of the present invention comprises a polyester whose main repeating unit is ethylene terephthalate, and the amount of the cyclic trimer increased by melting at a temperature of 290 ° C. for 60 minutes is not more than 0.30% by weight. The content of the trimer is 0.35% by weight or less, the average density of the polyester chips is 1.3950 g / cm ³ or more, the density of the outer layer of the chips is 1.4030 g / cm ³ or less, and the chips are The difference in density between the center layer and the outer layer is 0.001
It is a polyester of 5 to 0.0050 g / cm ³ .

In the present invention, the “outer layer” refers to a layer having a thickness of 0.5 mm inward from the outer surface of the chip, and the “center layer” has one side centered on the center of the chip. A layer having a shape of a 0.5 mm cubic cube.

At the time of solid-phase polymerization of polyester, low-molecular compounds such as water and ethylene glycol generated inside the chip by the polycondensation reaction diffuse into the chip surface layer and are removed from the chip surface, whereby the reaction proceeds. The molecular weight increases. In addition, during solid phase polymerization, crystallization of the chip is progressing, and heat due to crystallization is generated inside the chip,
This is accumulated inside the chip due to poor thermal conductivity of polyester. For this reason, since the temperature inside the chip is inevitably higher, the crystallinity inside the chip, especially the central layer, becomes higher than the crystallinity of the outer layer, and the crystal inside the chip becomes denser. . In order to express such a degree of crystallization or a state of a crystal, a value of density is generally used. Since the crystals formed inside the chip are dense and the amount thereof is large, they are less likely to melt than the crystals formed in the outer layer. Therefore, when molding under the condition that the crystal of the outer layer melts, the crystal inside does not completely melt, and this acts as a crystal nucleus.

When the polyester of the present invention is melted at a temperature of 290 ° C. for 60 minutes, the amount of cyclic trimer increased by 0.30
It is necessary to be less than the weight%. The amount of increase of the cyclic trimer is preferably 0.2% by weight or less, more preferably 0.1% by weight.
1% by weight or less. If the increase of the cyclic trimer when melted at a temperature of 290 ° C. for 60 minutes exceeds 0.30% by weight, the amount of the cyclic trimer increases when the polyester is melt-molded, and the amount of the cyclic trimer increases on the surface of the heating mold. Oligomer adhesion sharply increases, and the transparency of the obtained hollow molded article and the like becomes extremely poor.

The content of the cyclic trimer of the polyester of the present invention is 0.35% by weight or less, preferably 0.34% by weight or less.
% By weight, more preferably 0.33% by weight or less. When a heat-resistant hollow molded article or the like is molded from the polyester of the present invention, heat treatment is performed in a heating mold. However, when the content of the cyclic trimer exceeds 0.35% by weight, heating is performed. Oligomer attachment to the mold surface increases sharply,
The transparency of the obtained hollow molded article and the like is extremely deteriorated.

The average density of the polyester chips of the present invention is not less than 1.3950 g / cm ³ , preferably not less than 1.3.
396 g / cm ³ or more, more preferably 1.397 g
/ Cm ³ or more. When the average density is less than 1.395 g / cm ³ , the content of the cyclic trimer does not decrease to 0.35% by weight or less.

The density of the outer layer of the polyester chip of the present invention is 1.4030 g / cm ³ or less, preferably 1.402 g / cm ³ or less. Outer layer density is 1.4
If it exceeds 030 g / cm ³ , the crystallinity inside the chip will be too high, and the crystals will not completely melt during melt molding and will remain as crystal nuclei. For this reason, the crystallization rate at the time of heating becomes faster, and the crystallization of the plug portion of the hollow molded body becomes excessive, and the shrinkage amount of the plug portion does not fall within the specified value range, so that the cap portion of the plug portion is defective. As a result, leakage of contents occurs, and the preform for hollow molding becomes white, so that normal stretching becomes impossible.

The difference in density between the center layer and the outer layer of the polyester chip of the present invention is 0.0015 to 0.0050 g.
/ Cm ³ , preferably 0.0018 to 0.0045 g /
cm ³ , more preferably 0.0020 to 0.0040
g / cm ³ . When the difference between the density of the center layer and the outer layer of the chip is less than 0.0015 g / cm ³ , crystals are easily melted when the molded body is melt-formed, and crystal nuclei having a crystallization promoting action are not generated, The crystallization rate is very slow. Therefore, when the plug portion of the hollow molded article is crystallized, crystallization is insufficient, and the shrinkage of the plug portion does not fall within the specified value range, resulting in poor capping. On the other hand, the difference in density between the center layer and the outer layer of the chip is 0.0050 g.
If it exceeds / cm ³ , a dense crystal is formed inside the chip, and the crystallinity is too high, so that the crystal does not completely melt during melt molding and remains as a crystal nucleus. For this reason, the crystallization rate at the time of heating becomes faster, and the crystallization of the plug portion of the hollow molded body becomes excessive, and the shrinkage amount of the plug portion does not fall within the specified value range, so that the cap portion of the plug portion is defective. And leakage of the contents may occur. In addition, the preform for hollow molding is whitened, which makes normal stretching impossible,
Thickness unevenness occurs, and the crystallization rate is high, so that the obtained hollow molded article has poor transparency and large fluctuations in transparency.

The polyester of the present invention can be produced, for example, as follows. That is, pre-crystallization is performed by subjecting the prepolymer chips obtained by melt polycondensation to heat treatment at 120 to 200 ° C. for 1 minute to 5 hours in an inert gas atmosphere or in an atmosphere of steam or an inert gas containing steam. Next, while continuously supplying the chips from the upper part of the tower-type continuous solid-state polymerization reactor, the chip temperature in the upper part and the central part of the tower is 195 to 215 ° C., and the chip temperature in the lower part is about 5 to 5 degrees above the above temperature. The temperature, flow rate and flow method of the inert gas are adjusted so as to lower the temperature by 15 ° C. or more, and the solid phase polymerization is performed for about 5 to 30 hours. By adjusting the temperature of the chip at the lower portion of the solid-state polymerization tower so as to be lower by about 5 to 15 ° C. as described above, an appropriate density difference between the center layer and the outer layer of the chip can be provided.

Next, the solid-state polymerized polyester chips were mixed with water, steam or steam so that the amount of the cyclic trimer increased by melting at a temperature of 290 ° C. for 60 minutes was 0.30% by weight or less. Contact treatment with the contained gas.

Examples of the hot water treatment method for chips include a method of immersing the chips in water and a method of spraying water on the chips with a shower. The treatment time is 5 minutes to 2 days, preferably 10 minutes to 1 day, more preferably 30 minutes to 10 hours, and the water temperature is 20 to 180 ° C, preferably 40 to 180 ° C.
To 150 ° C, more preferably 50 to 120 ° C.

The following is an example of a method for industrially performing water treatment, but the method is not limited thereto. The treatment method may be either a continuous method or a batch method, but a continuous method is preferable for industrial use.

When the water treatment of the polyester chips is performed in a batch system, a silo-type treatment tank may be used.
That is, the chips of the polyester are received in the silo in a batch system and water treatment is performed. Alternatively, it is also possible to receive the polyester chips in a rotary cylindrical treatment tank and perform water treatment while rotating the chips to make the contact with water more efficient.

When the water treatment of the polyester chips is performed in a continuous manner, the polyester chips can be continuously or intermittently received in the tower-type treatment tank from the top and subjected to water treatment. This conceptual diagram is shown in FIG.

The method of contacting the polyester chips with steam or a steam-containing gas is as follows.
Water vapor or a gas containing water vapor, preferably at a temperature of 50 to 110 ° C., is preferably supplied or present as water vapor in an amount of 0.5 g or more per kg of chips to contact the water vapor. The contact between the chip and the water vapor is usually performed for 10 minutes to 2 days, preferably for 20 minutes to 10 hours.

The following is an example of a method for industrially performing the contact treatment of polyester chips with steam or a steam-containing gas, but the method is not limited thereto. The processing method may be either a continuous method or a batch method.

When the contact treatment of the polyester chips with steam or a steam-containing gas is carried out in a batch system, a silo-type treatment apparatus may be used. That is, the chip is received in a silo, and a contact treatment is performed by supplying steam or a steam-containing gas in a batch system. Alternatively, the chip can be received in a rotary cylinder type contact processing device, and the contact processing can be performed while rotating the chip to make the contact more efficient.

When the polyester chips are subjected to the contact treatment with steam or a steam-containing gas in a continuous manner, the chips are continuously received from above in a tower-type treatment apparatus, and steam is continuously supplied in cocurrent or countercurrent to provide steam. Can be contacted.

As described above, after being treated with water, steam or a steam-containing gas, the polyester chips are drained with a draining device such as a vibrating sieve or a Simon Carter if necessary.
Transfer to the next drying step.

Drying of the polyester chips which have been subjected to contact treatment with water or steam can be carried out by a commonly used polyester drying treatment. As a method for continuous drying, a hopper-type through-air dryer that supplies chips from the upper portion and allows the drying gas to flow from the lower portion is usually used. As a method for reducing the amount of drying gas and drying efficiently, a rotary disk-type continuous dryer is used. Heating steam, heating medium, etc. are supplied to the rotating disk and the outer jacket while passing a small amount of drying gas. The chips can be heated and dried indirectly.

As a dryer for drying in a batch system, a double cone type rotary dryer is used, and drying can be performed under vacuum or while passing a small amount of drying gas under vacuum. Alternatively, the drying may be performed while passing a drying gas under atmospheric pressure. As the dry gas, atmospheric air may be used, but dry nitrogen and dehumidified air are preferred from the viewpoint of preventing a reduction in molecular weight due to hydrolysis or thermal oxidative decomposition of the polyester.

The content of diethylene glycol copolymerized in the polyester used in the present invention is preferably 1.5 to 5.0 mol%, more preferably 1.8 to 4.5 mol, of the glycol component forming the polyester. %, Particularly preferably 2.0 to 4.0 mol%. When the amount of diethylene glycol exceeds 5.0 mol%, the thermal stability is deteriorated, and the decrease in molecular weight at the time of molding is increased.
The increase in the acetaldehyde content and the formaldehyde content is undesirably large. When the diethylene glycol content is less than 1.5 mol%, the transparency of the obtained molded article tends to be low.

The acetaldehyde content of the polyester of the present invention is 5 ppm or less, preferably 4 ppm or less, more preferably 3 ppm or less, and the formaldehyde content is 5 ppm or less, preferably 4 ppm or less, more preferably 3 ppm or less. When the content of acetaldehyde is 5 ppm or more and the content of formaldehyde is 5 ppm or more, the contents such as containers molded from the polyester deteriorate in flavor and odor.

In the polyester production process, in the step of chipping the melt polycondensation polymer, the solid phase polymerization step, the step of transporting the melt polycondensation polymer chip or the solid phase polymerization polymer chip, etc., it was originally set at the time of granulation. Granules and powders which are considerably smaller than chips of a size are generated. In the present invention, such fine particles and powder having the same composition as the polyester chips are called fine. In the process of producing polyester, high-purity raw materials and auxiliary materials are used, and at the same time, filtration of molten polycondensation polymer, filtration of cooling water of polyester chips, filtration of water introduced from outside the system for water treatment of chips, the said chips Since measures are taken to prevent foreign substances and foreign substances other than the polyester used from being mixed by, for example, filtration of gas used for transportation of the fine particles, the fine can be free of foreign substances and foreign substances other than polyester. .

The content of such fines in the polyester is preferably 0.1 to 300 ppm, more preferably 0.2 to 250 ppm. Content is 0.1p
If it is less than pm, the crystallization speed becomes very slow, and the crystallization of the plug portion of the hollow molded body becomes insufficient. In addition, the stretch heat-fixing mold for forming the heat-resistant hollow molded article is heavily soiled, and the mold must be cleaned frequently to obtain a transparent hollow molded article. In addition, when it exceeds 300 ppm, the crystallization speed is increased, and the crystallization of the plug portion of the hollow molded body becomes excessive,
For this reason, since the shrinkage amount of the plug portion does not fall within the specified value range, the cap portion of the plug portion becomes defective and leakage of the content occurs, and the preform for hollow molding is whitened, so that normal stretching can be performed. Impossible.

In the present invention, the intrinsic viscosity of the fine polyester is usually 0.55 to 0.90, preferably 0.57 to 0.88, and more preferably 0.58 to 0.88.
0.87. When the intrinsic viscosity is less than 0.55, the transparency of the obtained molded body is deteriorated, and the shrinkage of the plug portion becomes too large. Further, it is preferable that the intrinsic viscosity is the same as the intrinsic viscosity of the polyester chip or 0.03 higher than the intrinsic viscosity of the polyester chip. The same composition as the polyester chip means that the fine copolymerization component and the content of the copolymerization component are the same as the polyester chip.

In the present invention, as a method of adjusting the fine content of the polyester to the above-mentioned range, a step of sieving a PET resin chip having a high fine content without passing through a sieving step and a fine removing step by an air flow are provided. In addition to the method of mixing PET resin chips having a very small fine content passed through at an appropriate ratio, the fine resin content can be adjusted by changing the size of the decoration in the fine removal step, and the sieving speed can be changed. Arbitrary methods can be used.

When the polyester chips are treated with water as described above, the following method is practical. First, in the water treatment step, it is preferable that at least a part of the water to be treated is water that has been discharged from the treatment tank, returned to the treatment tank, and used repeatedly. By reusing water, it is possible to control the amount of fine powder mixed into the treated water from outside the system, and it is easy to control the fine content of the polyester. The amount of fine powder mixed with water from outside the system is 0
Is used for water treatment, the fines attached to the polyester chips are washed away by
May be below. Furthermore, the amount of fine powder in the treated water is reduced to 10
It is preferable to perform the treatment while adjusting the concentration to be 00 ppm or less, preferably 500 ppm or less. Fine powder amount is 100
When water exceeding 0 ppm is used, the fine content of the polyester may exceed 300 ppm.

It is also possible to simultaneously use a saturated fatty acid monoamide, an unsaturated fatty acid monoamide, a saturated fatty acid bisamide, an unsaturated fatty acid bisamide and the like with the polyester of the present invention. Examples of the saturated fatty acid monoamide include lauric amide, palmitic amide, stearic amide, behenic amide and the like. Examples of unsaturated fatty acid monoamides include oleic acid amide, erucic acid amido ricinoleic acid amide, and the like. Examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylenebiscapric acid amide, ethylenebislauric acid amide, ethylenebisstearic acid amide,
Ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide and the like can be mentioned. Examples of the unsaturated fatty acid bisamide include ethylene bisoleic acid amide and hexamethylene bisoleic acid amide. Preferred amide compounds include saturated fatty acid bisamides and unsaturated fatty acid bisamides. The compounding amount of such an amide compound is in the range of 10 ppb to 1 × 10 ⁵ ppm.

The polyester of the present invention has a carbon number of 8 to
33 metal salt compounds of aliphatic monocarboxylic acids, such as naphthenic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid,
Lithium salts, sodium salts, potassium salts, magnesium salts, calcium salts, cobalt salts, and the like of saturated and unsaturated fatty acids such as montanic acid, melicic acid, oleic acid, and linoleic acid can be used together. The compounding amount of these compounds is in the range of 10 ppb to 300 ppm.

The polyester of the present invention can be preferably used as a packaging material such as a hollow molded article, a tray, a biaxially stretched film, a film for covering a metal can, and the like. Also,
The polyester of the present invention can also be used as one constituent layer of a multilayer molded article or a multilayer film.

The polyester of the present invention may contain, if necessary, a known ultraviolet absorber, a lubricant added from the outside or a lubricant internally deposited during the reaction, a release agent, a nucleating agent, a stabilizer, an antistatic agent, a pigment, and the like. And various other additives.

[0065]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.
The main method of measuring characteristic values in the present invention will be described below.

(1) Intrinsic Viscosity of Polyester (IV) Determined from the solution viscosity at 30 ° C. in a 1,1,2,2-tetrachloroethane / phenol (2: 3 weight ratio) mixed solvent.

(2) Diethylene glycol content (hereinafter referred to as [DEG content]) Decomposed with methanol, the DEG content was determined by gas chromatography, and expressed as a ratio (mol%) to the total glycol components.

(3) Acetaldehyde content (hereinafter referred to as “A
A) The sample / distilled water = 1 g / 2 mL was placed in a glass ampoule purged with nitrogen, the upper part was sealed, extracted at 160 ° C for 2 hours, and after cooling, the acetaldehyde in the extract was converted to a highly sensitive gas. The concentration was measured by chromatography and the concentration was expressed in ppm.

(4) Content of Polyester Cyclic Trimer (CT Content) A sample is dissolved in a mixed solution of hexafluoroisopropanol / chloroform, and further diluted with chloroform. After adding methanol to precipitate a polymer, the mixture is filtered. The filtrate was evaporated to dryness, made up to a constant volume with dimethylformamide, and the cyclic trimer composed of ethylene terephthalate units was quantified by liquid chromatography.

(5) Amount of increase in cyclic trimer when polyester is melted (ΔCT amount) 3 g of dried polyester chips are placed in a glass test tube, and immersed in a 290 ° C. oil bath for 60 minutes under a nitrogen atmosphere. Let melt. The increased amount of the cyclic trimer at the time of melting was determined by the following equation. Cyclic trimer increase during melting (% by weight) = cyclic trimer content after melting (% by weight) -cyclic trimer content before melting (% by weight)

(6) Sampling of the center layer and outer layer of the polyester chip From the chip surface except the cut surface at the time of forming the chip, cut a 0.5 mm thick section from the outer surface with a cutter, and then cut the cut surface. The corresponding ends are cut to obtain the outer layer sample. In addition, two planes parallel to the cutting plane at the time of chip formation have a width of 0.1 mm so that the center of the chip is included in the center.
A 5 mm pillar is cut from the center of the chip. Next, a cube having a side of 0.5 mm is cut out from this pillar so that the center of the chip is in the middle, and used as a sample of the center layer.
From 10 arbitrary chips, the central layer and the outer layer were sampled for each chip and subjected to density measurement.

(7) Measurement of Fine Content About 0.5 kg of the resin was placed on a sieve (diameter 30 cm) having a wire mesh having a nominal size of 1.7 mm according to JIS-Z-8801, and 0.1% of An aqueous solution of a cationic surfactant (alkyltrimethylammonium chloride) at 2 L /
While applying a shower at a flow rate of 1 minute, the total amplitude width is about 7c
m, 60 reciprocations / 1 minute for 1 minute. This operation was repeated to sieve a total of 30 kg of the resin. The sieved fines were collected by filtration with a surfactant aqueous solution using a 1G1 glass filter (pores 100 to 120 μm) manufactured by Iwaki Glass Co., Ltd., and washed with ion-exchanged water. This was dried together with the glass filter in a dryer at 100 ° C. for 2 hours, cooled, and weighed. The same operation of washing and drying with ion-exchanged water was repeated again to confirm that the weight became constant, and the weight of the glass filter was subtracted from this weight to obtain a fine weight. The fine content is the fine amount / the weight of the total resin sieved,
It is.

(8) Average Density of Polyester Chip and Density of Center Layer and Outer Layer The density was measured at 30 ° C. using a density gradient tube of a mixed solution of calcium nitrate / water. The density of any ten chips was measured, and the average was taken as the average density. Further, the difference between the densities of the corresponding central layer and the outer layer from the same chip was determined, and the average value was defined as the density difference between the central layer and the outer layer.

(9) Density of parison stopper part The density was measured at 30 ° C. using a density gradient tube of a calcium nitrate / water mixed solution.

(10) Haze (% haze) and haze spots A molded article (thickness: 5 mm) of the following (13) and the following (14)
A sample was cut out from the body (thickness: about 0.4 mm) of the hollow molded article of Example 1 and measured by a haze meter manufactured by Nippon Denshoku Co., Ltd. Further, the haze of a molded plate (thickness: 5 mm) molded continuously 10 times was measured, and the haze unevenness was determined as follows. Haze spot = maximum value of haze / minimum value of haze

(11) Density increase due to heating of parison plug The parison plug is heated to 60% by a homemade infrared heater.
After heat treatment for 2 seconds, a sample was taken from the top surface and the density was measured.

(12) Variation in thickness of bottle Four samples (3 cm × 3 cm) were randomly cut from the center of the body of the hollow molded article of (14) described later, and the thickness was measured with a digital thickness gauge (the same sample). Were measured at five points, and the average was taken as the sample thickness.) The thickness unevenness was determined as follows. Thickness unevenness = maximum thickness / minimum thickness

(13) Forming of Stepped Forming Plate The dried polyester was prepared using M-150C manufactured by Meiki Seisakusho Co., Ltd.
(DM) Using an injection molding machine, molding was performed at a cylinder temperature of 290 ° C. using a stepped flat mold cooled to 10 ° C. The resulting stepped plate was 2, 3, 4, 5, 6, 7,
A plate with a thickness of about 3 cm x about 5 cm square with a thickness of 8, 9, 10, and 11 mm is provided in a stepwise manner.
46 g. A plate having a thickness of 5 mm was used for measuring haze (% haze).

(14) Evaluation of Mold Stain The polyester was dried with a dryer using dehumidified air, and a preform was molded at a resin temperature of 295 ° C. using an M-150C (DM) injection molding machine manufactured by Meiki Seisakusho. . The plug portion of this preform was heated and crystallized with a home-made plug portion crystallizing device, and then biaxially stretched and blow-molded using an LB-01 stretch blow molding machine manufactured by Corpoplast Co., Ltd.
It was heat-set for 10 seconds in a mold set at ℃ to obtain a 500 cc hollow molded body (the body was circular). The stretch blow molding was continuously performed under the same conditions, and the stain on the mold was evaluated by the number of moldings until the transparency of the molded body was impaired by visual judgment. Further, as a sample for haze measurement, a body portion of a molded body after continuous molding 5,000 times was provided.

(15) Evaluation of Leakage of Contents from Hollow Molded Article The hollow molded article molded in (14) above was filled with hot water at 90 ° C., capped by a capping machine, the container was turned down, and the contents were left to stand. The leakage of things was checked. The deformation of the plug after capping was also examined.

[0081]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A melt-polycondensed polyethylene terephthalate prepolymer having an IV of 0.55 dL / g was continuously crystallized at about 155 ° C. for 3 hours under a nitrogen gas flow, and then a column-type solid-state polymerization apparatus was prepared. At a temperature of 208 ° C. and a lower temperature of 20 ° C.
Solid phase polymerization was performed at 0 ° C. for (20) hours to obtain a solid phase polymerized polyester.

This polyethylene terephthalate (hereinafter referred to as “polyethylene terephthalate”)
"PET") was treated with water as follows. PE
For the water treatment of the chips of T, the apparatus shown in FIG. 1 is used. The raw material chip supply port (1) at the upper part of the processing tank, the overflow discharge port (2) located at the upper limit level of the processing water in the processing tank, and the lower part of the processing tank An outlet (3) for a mixture of PET chips and treated water, treated water discharged from the overflow outlet, treated water discharged from the treatment tank, and a draining device discharged from the outlet at the bottom of the treatment tank ( The treated water passed through 4) is again sent to the water treatment tank via the fine powder removing device (5) whose filter medium is a continuous filter of 30 μm made of paper, and the treated water from which these fine powders have been removed. Using a tower-type treatment tank with an internal capacity of about 500 liters equipped with an inlet (7), an adsorption tower (8) for adsorbing acetaldehyde in the treated water from which fine powder has been removed, and an inlet (9) for new ion-exchanged water. did.

PET chips were continuously introduced into the water treatment tank controlled at a temperature of 95 ° C. at a rate of 50 kg / hour from the supply port (1) at the top of the treatment tank, and the treated water having a fine powder content of about 100 ppm was added. 50k as PET chips from the outlet (3) at the bottom of the treatment tank in 4 hours of water treatment using
It was continuously withdrawn with the treated water at a rate of g / hour. The fine content of the obtained PET was about 13 ppm. In addition, the amount of fine powder in the treated water is 1000 parts of treated water that has passed through a filter having a nominal size of 850 μm according to JIS (JIS-Z-8801) from the treated water discharge port of the treated layer.
mL is collected, filtered through a 1G1 glass filter (pores 100 to 120 μm) manufactured by Iwaki Glass Co., Ltd., dried at 100 ° C. for 2 hours, cooled at room temperature, and then weighed to calculate.

The intrinsic viscosity of the obtained PET is 0.74 dL.
/ G, DEG content is 2.5 mol%, cyclic trimer content is 0.30 wt%, cyclic trimer increase is 0.05 wt%, average density is 1.4030 g / cm ³ , The density of the chip outer layer is 1.4017 g / cm ³ , the density difference between the chip center layer and the outer layer is 0.0020 g / cm ³ , and the AA content is 3.0.
ppm and fine content were 13 ppm. The residual amount of Ge measured by atomic absorption analysis is 55 ppm,
The residual amount of P was 37 ppm.

This PET was evaluated with a molded plate and a biaxially stretched bottle. Table 1 shows the results. The haze of the molded plate is 2.8%, and the density of the plug portion is 1.370 g.
/ Cm ³ , which is a value that is not a problem, and continuous stretch blow molding of 5,000 or more was performed, but no mold contamination was observed.
The transparency of the bottle was also good. Also, there was no problem in the leakage test of the contents, and there was no deformation of the plug portion.
The obtained bottle had favorable body haze of 0.7%, haze unevenness of 1.1 and thickness unevenness of 1.05. In addition, the number of moldings up to mold contamination was 10,000, which was no problem.
The AA content of the bottle was 15.4 ppm, a value without a problem.

(Example 2) Using the same prepolymer as in Example 1, the temperature of the upper part and the intermediate part during the solid-phase polymerization was set to 2
Example 1 except that the lower temperature was changed to 10 ° C. and the lower temperature to 200 ° C.
, And then water treatment was performed under the same conditions. Table 1 shows the properties of the obtained PET, a molded plate formed from the PET, and a biaxially stretched bottle. The result was fine.

(Comparative Example 1) The same prepolymer as in Example 1 was used, except that the temperature of the upper, middle and lower parts during the solid phase polymerization was set to 200 ° C. to extend the solid phase polymerization time. Solid phase polymerization was performed under the same conditions as in 1, and then water treatment was performed under the same conditions. Table 1 shows the properties of the obtained PET, a molded plate formed from the PET, and a biaxially stretched bottle. The intrinsic viscosity of the obtained PET is 0.74 dL / g, the content of DEG is 2.5 mol%, the content of the cyclic trimer is 0.55 wt%, and the increase in the cyclic trimer is 0.07 wt%. The average density is 1.3943 g / cm ³ and the density of the outer layer of the chip is 1.39.
32 g / cm ³ , the density difference between the chip center layer and the outer layer is 0.0
013 g / cm ³ , AA content was 4.8 ppm, and fine content was 15 ppm. Further, the haze of the molded plate was as good as 2.0%, but the density of the plug portion was 1.357 g /.
cm ^{3, which} is an insufficient value, and continuous stretch blow molding of 5,000 or more was carried out.
There was a problem of 000 times, and the transparency of the bottle was also poor. In addition, in the leakage test of the contents, leakage of the contents was observed, and deformation of the plug portion was also observed. The body haze of the obtained bottle was as poor as 9.4%.

Comparative Example 2 The same prepolymer as in Example 1 was used, except that the temperature of the upper, middle and lower parts during the solid phase polymerization was set to 217 ° C. to shorten the solid phase polymerization time. Solid phase polymerization was performed under the same conditions as in Example 1, and then water treatment was performed under the same conditions as in Example 1 except that treated water having a different fine powder content was used. Table 1 shows the properties of the obtained PET, a molded plate formed from the PET, and a biaxially stretched bottle. The intrinsic viscosity of the obtained PET is 0.74 dL / g, the content of DEG is 2.5 mol%, the content of the cyclic trimer is 0.29 wt%, and the increase in the cyclic trimer is 0.07 wt%. The average density is 1.4140 g / cm ³ and the density of the outer layer of the chip is 1.41.
03 g / cm ³ , the density difference between the chip center layer and the outer layer is 0.0
058 g / cm ³ , AA content was 2.6 ppm, and fine content was about 450 ppm. Table 1 shows the results of the molding evaluation and the bottle molding evaluation. The deformation of the plug and the leakage of the contents were examined, and leakage of the contents was observed. The continuous stretch blow molding of 5,000 or more was performed, but the number of moldings up to mold contamination was 6,000, and the bottle was poor in transparency.

(Comparative Example 3) Using the same prepolymer as in Example 1, the temperature of the upper and middle parts during the solid phase polymerization was set to 21.
Solid phase polymerization was performed under the same conditions as in Example 1 except that the solid phase polymerization time was shortened by setting the temperature at 8 ° C. and the temperature at the lower part to 203 ° C., and then water treatment was performed under the same conditions as in Example 1. Table 1 shows the properties of the obtained PET, a molded plate formed from the PET, and a biaxially stretched bottle. The intrinsic viscosity of the obtained PET is 0.75 dL / g, the content of DEG is 2.5 mol%, the content of the cyclic trimer is 0.33 wt%, and the increase in the cyclic trimer is 0.06 wt%. , The average density is 1.4072 g / cm ³ ,
The density of the chip outer layer was 1.4060 g / cm ³ , the difference in density between the chip center layer and the outer layer was 0.0019 g / cm ³ , the AA content was 2.8 ppm, and the fine content was about 20 ppm. Table 1 shows the results of the molding evaluation and the bottle molding evaluation. The deformation of the spout and leakage of the contents were examined, and leakage of the contents was observed. The continuous stretch blow molding of 5,000 or more was carried out, but the number of moldings up to mold contamination was 6000, and the bottle was poor in transparency.

[0091]

[Table 1]

[0092]

According to the polyester of the present invention, the crystallization controllability at the time of melt molding and the long-term continuous formability are excellent, and the hollow molded article, sheet-like material and stretched film obtained therefrom have transparency, It has good thermal dimensional stability, and particularly, the shrinkage rate of the plug portion of the hollow molded body is in an appropriate range, and when used as a liquid container, residual off-tastes and off-flavors are hardly generated.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus used for producing the polyester of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material chip supply port 2 Overflow discharge port 3 Polyester chip and treated water discharge port 4 Drainer 5 Fine powder removal device 6 Piping 7 Treated water inlet 8 Adsorption tower 9 Ion exchange water inlet

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 67:00 B29K 67:00 B29L 7:00 B29L 7:00 C08L 67:02 C08L 67:02 ( 72) Inventor Yoshitaka Eto 20F term of 248 Takagi, Shiga-cho, Shiga-gun, Shiga Pref. AC01 AD10 AE01 AE03 BA03 BF09 CB06A HA01 HB01 KB02 KC06 KE12 KF02 KF04 KH03 KH05

Claims (9)

[Claims] 1. A polyester in which the main repeating unit is ethylene terephthalate and the amount of increase of the cyclic trimer when melted at a temperature of 290 ° C. for 60 minutes is 0.30% by weight or less. The content is 0.35% by weight or less, and the average density of the polyester chips is 1.3.
950 g / cm ³ or more, and the density of the outer layer of the chip is 1.4
030 g / cm ³ or less, and the difference in density between the center layer and the outer layer of the chip is 0.0015 to 0.0050 g / cm ³ . 2. The content of copolymerized diethylene glycol is one of the glycol components constituting the polyester.
The polyester according to claim 1, wherein the amount is 5 to 5.0 mol%. 3. The polyester according to claim 1, wherein the acetaldehyde content is 5 ppm or less. 4. A polyester chip having a fineness of polyester having the same composition as that of the chip is 0.1 to 300 pp.
The polyester according to claim 1, 2 or 3, wherein m is contained. 5. A chip formed after the polycondensation is treated with treated water satisfying the following conditions (a) and (b) in a treatment tank.
Polyester according to 2, 3 or 4. (A) Temperature of 40 to 120 ° C (b) Treated water including wastewater from the treatment tank 6. A chip formed after the polycondensation is treated in a treatment tank with treated water satisfying the following condition (c).
Or the polyester according to 5. (C) Treated water having a fine powder content of 1000 ppm or less 7. A hollow molded article obtained by molding the polyester according to claim 1, 2, 3, 4, 5, or 6. 8. A sheet formed by molding the polyester according to claim 1, 2, 3, 4, 5 or 6. 9. A stretched film obtained by stretching the sheet material according to claim 8 in at least one direction.